#include <bits/stdc++.h>

using namespace std;

long countArray(int n, int k, int x) {
   int u;
    int a[n];
    a[0]=1;
    a[n]=x;
    if(n==3)
        return 1;
    else if(n==4)
        return 3;
    else
    {
        u=n-1;
        return(((u*(u+1))/2)-1);
    }
    
    
}

int main() {
    int n;
    int k;
    int x;
    cin >> n >> k >> x;
    long answer = countArray(n, k, x);
    cout << answer << endl;
    return 0;
}